The present invention relates to reversible screwdrivers, and relates more particularly to the ratchet transmission control mechanism of a screwdriver.
Various reversible screwdrivers are well known, and popularly accepted. These reversible screwdrivers commonly use a ratchet mechanism and a switch for controlling the transmission of driving power from the handle to the shaft. When the switch is shifted leftwards, the first stop plate of the ratchet mechanism is forced into engagement with the ratchet on the shaft, and the second stop plate thereof is forced away from the ratchet, therefore the shaft can be turned by the handle clockwise. When the switch is shifted rightwards, the second stop plate of the ratchet mechanism is forced into engagement with the ratchet on the shaft, and the first stop plate is forced away from the ratchet, therefore the shaft can be turned by the handle counter-clockwise. When the switch is shifted to the middle position, the first stop plate and the second stop plate are respectively forced into engagement with the ratchet, and therefore the shaft can be turned by the handle in both ways. This structure of screwdriver is complicated. Furthermore, the switch tends to be shifted over the desired position during the adjustment of the control mode.